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Lasers and Laser Optics|341 Article(s)
Laser transverse modes of spherical resonators: a review [Invited]|On the Cover
Y. F. Chen, C. C. Lee, C. H. Wang, and M. X. Hsieh
The study of structured laser beams has been one of the most active fields of research for decades, particularly in exploring laser beams with orbital angular momentum. The direct generation of structured beams from laser resonators is deeply associated with the formation of transverse modes. The wave representations of transverse modes of spherical cavities are usually categorized into Hermite–Gaussian (HG) and Laguerre–Gaussian (LG) modes for a long time. Enormous experimental results have revealed that the generalized representation for the transverse modes is the Hermite–LG (HLG) modes. We make a detailed overview for the theoretical description of the HLG modes from the representation of the spectral unitary group of order 2 in the Jordan–Schwinger map. Furthermore, we overview how to derive the integral formula for the elliptical modes based on the Gaussian wave-packet state and the inverse Fourier transform. The relationship between the HLG modes and elliptical modes is linked by the quantum Fourier transform. The most striking result is that the HLG modes can be exactly derived as the superposition of the elliptical modes without involving Hermite and Laguerre polynomials. Finally, we discuss the application of the HLG modes in characterizing the propagation evolution of the vortex structures of HG beams transformed by an astigmatic mode converter. This overview certainly provides not only a novel formula for transverse modes, but also a pedagogical insight into quantum physics. The study of structured laser beams has been one of the most active fields of research for decades, particularly in exploring laser beams with orbital angular momentum. The direct generation of structured beams from laser resonators is deeply associated with the formation of transverse modes. The wave representations of transverse modes of spherical cavities are usually categorized into Hermite–Gaussian (HG) and Laguerre–Gaussian (LG) modes for a long time. Enormous experimental results have revealed that the generalized representation for the transverse modes is the Hermite–LG (HLG) modes. We make a detailed overview for the theoretical description of the HLG modes from the representation of the spectral unitary group of order 2 in the Jordan–Schwinger map. Furthermore, we overview how to derive the integral formula for the elliptical modes based on the Gaussian wave-packet state and the inverse Fourier transform. The relationship between the HLG modes and elliptical modes is linked by the quantum Fourier transform. The most striking result is that the HLG modes can be exactly derived as the superposition of the elliptical modes without involving Hermite and Laguerre polynomials. Finally, we discuss the application of the HLG modes in characterizing the propagation evolution of the vortex structures of HG beams transformed by an astigmatic mode converter. This overview certainly provides not only a novel formula for transverse modes, but also a pedagogical insight into quantum physics.
Chinese Optics Letters
- Publication Date: Sep. 10, 2020
- Vol. 18, Issue 9, 091404 (2020)
Broadband photochromic effect and photoluminescence modulation in rare-earth-doped (Pb,La)(Zr,Ti)O3 ceramics
Long Xu, Ruiqi Zhu, and Caixia Xu
The broadband photochromic effect on undoped and rare-earth-doped lead lanthanum zirconate titanate (PLZT) ceramics was studied under the illumination of ultraviolet light at 360 nm. The photocarriers’ trapping and detrapping processes of thermal disconnected traps played the vital role in both darkening and bleaching processes. The interaction between photocarrier traps and rare-earth ion energy levels was demonstrated, which influenced the photochromatic darkening performance greatly. The transformation of photoluminescence spectra in Er3+-doped PLZT ceramics also improved the physical picture of the trap’s distribution of the materials. This work could be used to modulate the photoluminescence and lasing behavior. The broadband photochromic effect on undoped and rare-earth-doped lead lanthanum zirconate titanate (PLZT) ceramics was studied under the illumination of ultraviolet light at 360 nm. The photocarriers’ trapping and detrapping processes of thermal disconnected traps played the vital role in both darkening and bleaching processes. The interaction between photocarrier traps and rare-earth ion energy levels was demonstrated, which influenced the photochromatic darkening performance greatly. The transformation of photoluminescence spectra in Er3+-doped PLZT ceramics also improved the physical picture of the trap’s distribution of the materials. This work could be used to modulate the photoluminescence and lasing behavior.
Chinese Optics Letters
- Publication Date: Sep. 10, 2020
- Vol. 18, Issue 9, 091403 (2020)
Experimental investigation on residual reflectance of Nd:glass amplifier edge cladding
Junjiang Hu, Liyan Zhang, Jiachuan Ni, Tao Meng, Lei Wen, Youkuo Chen, Jingping Tang, Biao Wang, Shubin Chen, Wei Chen, and Lili Hu
A novel four light ray path test method for measuring residual reflectance has been presented. Residual reflectance spatial distribution at a cladding interface was measured using the technique. Residual reflectance could be on the order of 10?5 by matching the refractive index of Nd:glass, polymer, and cladding glass and eliminating defects in the adhesive layer. Residual reflection spatial distribution appears to be similar to Newton rings due to the edge surface flatness. The relationship between the residual reflectance and the edge surface flatness was discussed, and the results revealed that the edge surface flatness is very important during the cladding process. A novel four light ray path test method for measuring residual reflectance has been presented. Residual reflectance spatial distribution at a cladding interface was measured using the technique. Residual reflectance could be on the order of 10?5 by matching the refractive index of Nd:glass, polymer, and cladding glass and eliminating defects in the adhesive layer. Residual reflection spatial distribution appears to be similar to Newton rings due to the edge surface flatness. The relationship between the residual reflectance and the edge surface flatness was discussed, and the results revealed that the edge surface flatness is very important during the cladding process.
Chinese Optics Letters
- Publication Date: Sep. 10, 2020
- Vol. 18, Issue 9, 091402 (2020)
Power and spectral analyses in diode-pumped c-cut Pbnm Tm:YAP laser
Jacek Kwiatkowski
Detailed power and spectral analysis of a diode-pumped c-cut Pbnm 3 at.% Tm-doped yttrium aluminum perovskite (Tm:YAP) laser in a continuous wave (CW) operation is presented. The laser was experimentally examined in terms of the dependence on the transmittance and radius of curvature of the output coupling mirrors. At room temperature, for an output coupling transmission of 10.8%, the maximum output power of 6.35 W was obtained under a total absorbed pump power of 13.67 W with an optical-to-optical conversion efficiency of 46.5%. The highest slope efficiency of 60.4% was indicated. A detailed spectral analysis was presented. For its dependence on output coupler transmission, the Tm:YAP laser generates wavelengths at approximately 1940 nm or 1990 nm. Detailed power and spectral analysis of a diode-pumped c-cut Pbnm 3 at.% Tm-doped yttrium aluminum perovskite (Tm:YAP) laser in a continuous wave (CW) operation is presented. The laser was experimentally examined in terms of the dependence on the transmittance and radius of curvature of the output coupling mirrors. At room temperature, for an output coupling transmission of 10.8%, the maximum output power of 6.35 W was obtained under a total absorbed pump power of 13.67 W with an optical-to-optical conversion efficiency of 46.5%. The highest slope efficiency of 60.4% was indicated. A detailed spectral analysis was presented. For its dependence on output coupler transmission, the Tm:YAP laser generates wavelengths at approximately 1940 nm or 1990 nm.
Chinese Optics Letters
- Publication Date: Sep. 10, 2020
- Vol. 18, Issue 9, 091401 (2020)
High-repetition-rate pulsed fiber laser based on virtually imaged phased array
Xuanjuan Chen, Yuxin Gao, Jiamin Jiang, Meng Liu, Aiping Luo, Zhichao Luo, and Wencheng Xu
High-repetition-rate (HRR) pulsed fiber lasers have attracted much attention in various fields. To effectively achieve HRR pulses in fiber lasers, dissipative four-wave-mixing mode-locking is a promising method. In this work, we demonstrated an HRR pulsed fiber laser based on a virtually imaged phased array (VIPA), serving as a comb filter. Due to the high spectral resolution and low polarization sensitivity features of VIPA, the 30 GHz pulse with high quality and high stability could be obtained. In the experiments, both the single-waveband and dual-waveband HRR pulses were achieved. Such an HRR pulsed fiber laser could have potential applications in related fields, such as optical communications. High-repetition-rate (HRR) pulsed fiber lasers have attracted much attention in various fields. To effectively achieve HRR pulses in fiber lasers, dissipative four-wave-mixing mode-locking is a promising method. In this work, we demonstrated an HRR pulsed fiber laser based on a virtually imaged phased array (VIPA), serving as a comb filter. Due to the high spectral resolution and low polarization sensitivity features of VIPA, the 30 GHz pulse with high quality and high stability could be obtained. In the experiments, both the single-waveband and dual-waveband HRR pulses were achieved. Such an HRR pulsed fiber laser could have potential applications in related fields, such as optical communications.
Chinese Optics Letters
- Publication Date: Jul. 10, 2020
- Vol. 18, Issue 7, 071403 (2020)
Sub-10-fs pulse generation from a blue laser-diode-pumped Ti:sapphire oscillator|Editors' Pick
Han Liu, Geyang Wang, Jianwang Jiang, Wenlong Tian, Dacheng Zhang, Hainian Han, Shaobo Fang, Jiangfeng Zhu, and Zhiyi Wei
Pulses as short as 8.1 fs were generated from a blue laser-diode-pumped Kerr-lens mode-locked Ti:sapphire oscillator, with an average power of 27 mW and a repetition rate of 120.6 MHz. The full width at half-maximum exceeds 146 nm, benefitting from the dispersion management by a combination of a low-dispersion fused silica prism pair and a series of double-chirped mirrors. To the best of our knowledge, this is the first time to generate sub-10-fs pulses from a laser diode directly pumped Ti:sapphire oscillator. Pulses as short as 8.1 fs were generated from a blue laser-diode-pumped Kerr-lens mode-locked Ti:sapphire oscillator, with an average power of 27 mW and a repetition rate of 120.6 MHz. The full width at half-maximum exceeds 146 nm, benefitting from the dispersion management by a combination of a low-dispersion fused silica prism pair and a series of double-chirped mirrors. To the best of our knowledge, this is the first time to generate sub-10-fs pulses from a laser diode directly pumped Ti:sapphire oscillator.
Chinese Optics Letters
- Publication Date: Jul. 10, 2020
- Vol. 18, Issue 7, 071402 (2020)
25 Gb/s directly modulated ground-state operation of 1.3 μm InAs/GaAs quantum dot lasers up to 75°C
Zhongkai Zhang, Zunren Lü, Xiaoguang Yang, Hongyu Chai, Lei Meng, and Tao Yang
We report 25 Gb/s high-speed directly modulated ground-state operation of 1.3 μm InAs/GaAs quantum dot (QD) lasers grown by molecular beam epitaxy. The active region of the lasers consists of eight layers of p-doped InAs QDs with high uniformity and density. Ridge-waveguide lasers with a 3-μm-wide and 300-μm-long cavity show a low threshold current of 14.4 mA at 20°C and high temperature stability with a high characteristic temperature of 1208 K between 20°C and 70°C. Dynamic response measurements demonstrate that the laser has a 3 dB bandwidth of 7.7 GHz at 20°C and clearly opened eye diagrams even at high temperatures up to 75°C under a 25 Gb/s direct modulation rate. We report 25 Gb/s high-speed directly modulated ground-state operation of 1.3 μm InAs/GaAs quantum dot (QD) lasers grown by molecular beam epitaxy. The active region of the lasers consists of eight layers of p-doped InAs QDs with high uniformity and density. Ridge-waveguide lasers with a 3-μm-wide and 300-μm-long cavity show a low threshold current of 14.4 mA at 20°C and high temperature stability with a high characteristic temperature of 1208 K between 20°C and 70°C. Dynamic response measurements demonstrate that the laser has a 3 dB bandwidth of 7.7 GHz at 20°C and clearly opened eye diagrams even at high temperatures up to 75°C under a 25 Gb/s direct modulation rate.
Chinese Optics Letters
- Publication Date: Jul. 10, 2020
- Vol. 18, Issue 7, 071401 (2020)
Parallel registration algorithm with arbitrary affine transformation
Qin Shu, Xiuli He, Chang Wang, and Yunxiu Yang
The point clouds scanned by a 3D laser scanner may be affine transformed when the size and posture of the objects being scanned are different. This type of problem is common, but few algorithms can solve it. Therefore, this Letter proposes a parallel registration algorithm. The algorithm eliminates the effects of the affine matrix in the point cloud, based on a simple whitening operation. Moreover, it also has strong anti-noise performance. The algorithm proposed in this Letter is not only simple in structure, but also shows excellent effects in practical applications and simulations. The point clouds scanned by a 3D laser scanner may be affine transformed when the size and posture of the objects being scanned are different. This type of problem is common, but few algorithms can solve it. Therefore, this Letter proposes a parallel registration algorithm. The algorithm eliminates the effects of the affine matrix in the point cloud, based on a simple whitening operation. Moreover, it also has strong anti-noise performance. The algorithm proposed in this Letter is not only simple in structure, but also shows excellent effects in practical applications and simulations.
Chinese Optics Letters
- Publication Date: Jul. 10, 2020
- Vol. 18, Issue 7, 071001 (2020)
21.2 kW, 1.94 times diffraction-limit quasi-continuous-wave laser based on a multi-stage, power-scalable and adaptive optics controlled Yb:YAG master-oscillator-power-amplifier system
Lei Huang, Yamin Zheng, Yading Guo, Lin Zhang, Chuang Sun, and Xiaojun Wang
A 21.2 kW, 1.94 times the diffraction-limit quasi-continuous-wave laser is presented in this Letter based on a multi-stage, power-scalable Yb:YAG master-oscillator-power-amplifier (MOPA) system under adaptive optics (AO) control. The output laser of the MOPA system is a rectangular beam with a length-width ratio of 2:1, a 200 μs pulse duration, and a 1000 Hz repetition rate. With the AO control system, the beam quality of the laser is improved from 4.20 to 1.94 times the diffraction limit. To our knowledge, this is the best quality laser in the 20 kW class except for combined lasers. A 21.2 kW, 1.94 times the diffraction-limit quasi-continuous-wave laser is presented in this Letter based on a multi-stage, power-scalable Yb:YAG master-oscillator-power-amplifier (MOPA) system under adaptive optics (AO) control. The output laser of the MOPA system is a rectangular beam with a length-width ratio of 2:1, a 200 μs pulse duration, and a 1000 Hz repetition rate. With the AO control system, the beam quality of the laser is improved from 4.20 to 1.94 times the diffraction limit. To our knowledge, this is the best quality laser in the 20 kW class except for combined lasers.
Chinese Optics Letters
- Publication Date: Jun. 10, 2020
- Vol. 18, Issue 6, 061402 (2020)
Directly modulated active distributed reflector distributed feedback lasers over wide temperature range operation (−40 to 85°C)
Gonghai Liu, Gongyuan Zhao, Gong Zhang, Qiaoyin Lu, and Weihua Guo
We experimentally demonstrated that the distributed feedback (DFB) lasers with the active distributed reflector achieved a 25.8 Gb/s operation over a wide temperature range of ?40 to 85°C. The DFB lasers can achieve additional feedback from an active distributed reflector with accurately controlled phase, and single-mode yields are not related to the position of cleave. The threshold currents of the fabricated laser are 6 mA and 20 mA at ?40°C and 85°C, respectively. The side mode suppression ratio of the fabricated laser is above 50 dB at all temperatures. Transmissions of 25.8 Gb/s after 10 km single-mode fibers with clear eye openings and less than 0.8 dB power penalty over a wide temperature range have been demonstrated as well. We experimentally demonstrated that the distributed feedback (DFB) lasers with the active distributed reflector achieved a 25.8 Gb/s operation over a wide temperature range of ?40 to 85°C. The DFB lasers can achieve additional feedback from an active distributed reflector with accurately controlled phase, and single-mode yields are not related to the position of cleave. The threshold currents of the fabricated laser are 6 mA and 20 mA at ?40°C and 85°C, respectively. The side mode suppression ratio of the fabricated laser is above 50 dB at all temperatures. Transmissions of 25.8 Gb/s after 10 km single-mode fibers with clear eye openings and less than 0.8 dB power penalty over a wide temperature range have been demonstrated as well.
Chinese Optics Letters
- Publication Date: Jun. 10, 2020
- Vol. 18, Issue 6, 061401 (2020)
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